Руководство по PHP
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empty

(PHP 3, PHP 4, PHP 5 )

empty -- Determine whether a variable is empty

Description

bool empty ( mixed var)

empty() returns FALSE if var has a non-empty and non-zero value. In otherwords, "", 0, "0", NULL, FALSE, array(), var $var;, and objects with empty properties, are all considered empty. TRUE is returned if var is empty.

empty() is the opposite of (boolean) var, except that no warning is generated when the variable is not set. See converting to boolean for more information.

Пример 1. A simple empty() / isset() comparison.

<?php
$var = 0;

// Evaluates to true because $var is empty
if (empty($var)) {
    echo '$var is either 0, empty, or not set at all';
}

// Evaluates as true because $var is set
if (isset($var)) {
    echo '$var is set even though it is empty';
}
?>

Замечание: Поскольку это языковая конструкция, а не функция, она не может вызываться при помощи переменных функций

Замечание: empty() only checks variables as anything else will result in a parse error. In otherwords, the following will not work: empty(addslashes($name)).

See also isset(), unset(), array_key_exists(), count(), strlen(), and the type comparison tables.

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